Eat ur a$$ of! not literally. I had the same prob u did and i just started eating the right amount of protein and i grew some. I dont intake 4000 cals a day cuz i dont have the resources but i intake about 250 grams of protein daily and ive grown about 8lbs in 3 months. I got sick and lost 4 but hey thats life! Its not easy by any means. Just dont give up!